Human T-Cell Leukemia Virus Type II (HTLV-II) is considered to be an etiologic agent of hairy cell leukemia and its prevalence is increasing in the blood supply. Our long term objective is to produce an immunological assay to study its prevalence in the blood supply. This phase I proposal specifically aims to develop a recombinant DNA system to produce a portion of the envelope protein which is immunogenic. The approach to be used will involve the assembly of a synthetic gene coding for that portion of the envelope protein. The gene will be cloned and expressed in E. coli. High level expression of the desired product will enable phase II research to focus on the E. coli. fermentation scale-up and purification.